The invention relates to tire building machinery, especially machines that are used in guiding a piece of plystock along a pathway and marking the centerline of the plystock as it moves along the pathway.
At present, two stationay guides are used in conjunction with a scriber that is positioned midway between the guides just downstream from the guides to prevent the scriber from cutting through the plystock. Theoretically this should work, but, practically speaking it doesn't, since the width of the plystock varies and the plystock wanders laterally, so that the mark of the scriber may be off center as much as one inch. The invention is designed to provide a machine which will adapt to the wanderings of the plystock and variance in the width of the plystock to maintain the making of the plystock at its centerline midway between the opposing marginal edges of the plystock.